Print hammer impact tip

ABSTRACT

A centrally supported print hammer having an impact tip adaptable for striking type characters in more than one column on a rotating typedrum, the tip providing a concave surface curvature for engaging with one edge or a portion of a character prior to engaging with another edge or the remaining portion of the same character. The tip is formed with the surface curvature in a direction axially along the drum; that is, the surface is concave in a direction normal to the curvature of the drum, whereupon, at the moment of impact, the uneven force resulting from the tip&#39;&#39;s striking a character offset from the centralized driving force is compensated by the tip curvature to provide uniform print density.

United States Patent [72] lnventor Ronald E. Muterspaw Fairborn, Ohio [21 App]. No. 798,312 [22] Filed Feb. 11, 1969 [45] Patented Sept. 14, 1971 [73] Assignee The National Cash Register Company Dayton, Ohio 54] PRINT HAMMER IMPACT TIP 12 Claims, 7 Drawing Figs.

[52] US. Cl l01/93 [51] Int. CL B4lj 9/00 [50] Field olSearch 101/93, 109, 407, 94; 197/36 [56] Reference Cited UNITED STATES PATENTS 2,776,618 1/1957 Hartley 101/93 2,805,620 9/1957 Rosen et al.,. 101/93 2,862,592 12/1958 Redmond 197/36 3,090,297 5/1963 Wilkins et a1 101/93 Primary Examiner-William B. Penn Al1orne \-s-Louis A. Kline, Wilbert Hawk, Jr. and George J.

Muckenthaler ABSTRACT: A centrally supported print hammer having an impact tip adaptable for striking type characters in more than one column on a rotating typedrum, the tip providing a concave surface curvature for engaging with one edge or a portion of a character prior to engaging with another edge or the remaining portion of the same character. The tip is formed with the surface curvature in a direction axially along the drum; that is, the surface is concave in a direction normal to the curvature of the drum, whereupon, at the moment of impact, the uneven force resulting from the tips striking a character offset from the centralized driving force is compensated by the tip curvature to provide uniform print density oounb mum- PATENTED SEPI 41% FIG.3

INVENTOR RONALD E. MUTERSPAW HIS ATTORNEYS PRINT HAMMER IMPACT Ti'P BACKGROUND OF THE INVENTION In the highspeed printing art, it has been customary to provide a typedrum, continuously rotating, with the type characters arranged in columns around the drum, and a plurality of printing hammers located along a typeline and actuated individually so as to strike a character at an exact instant. Generally, a separate hammer has been provided for each column of characters on the typedrum, the hammers extending on a line along the drum and each hammer being fired by means of suitable solenoids or the like in a sequence as determined by the logic circuitry.

Recently, the prior art has shown the provision of print hammers which are sufficiently wide to span two or more columns of type characters. U.S. Pat. No. 3,128,693, issued Apr. 14, 1964, on the application of Francis V. Thiemann, shows a printer drum carrying a plurality of columns of type characters grouped so as to comprise a complete complement of contiguously arranged characters in each column, and a plurality of hammers wherein each hammer spans two or more columns. Spaces are provided between character columns, so that a group comprises an odd column and an even column in the case of the two-column-spanning hammer. Additionally, the prior art shows, in U.S. Pat. No. Re. 26,240, issued July 18, 1967, on the application of Carl 1. Wasserman, a highspeed printer with column-spanning hammers wherein the hammers can be moved laterally between two or more columns, this art also showing the blank spaces between the characters, so that a hammer strikes only one character at a time.

With regard to certain other printers, such as typewriters or the like, having curvature of the type characters on a typebar carrying more than one character and wherein one character is in a columnar line with the other, U.S. Pat. No. 660,287, issued Oct. 23, 1900, on the application of Daniel Briggs and William H. Shepard, and U.S. Pat. No. 2,862,592, issued Dec. 2, 1958, on the application of Carl E. Redmond, show removable character facings, the facings having a curvature conforming with that of the periphery of the associated platen.

One problem which has arisen with the use of a wider hammer so as to be capable of striking adjacent type characters, or one which spans two or more columns, is the difference in density across the width of a character when it is printed. In the case of a hammer spanning two columns, it is found that, while one portion of the impact side of the hammer tip strikes the raised surface of a character (the characters being etched on the drum by a well-known process), the other portion of that side is permitted to move slightly farther due to a blank space in the adjacent column. It is required, of course, that the hammer strike only one character at a time, so the spacing and arrangement of characters on the drum must be compatible with the shape and area of the hammer tip. Because the wide-faced hammer is centrally supported and driven, the raised surface of the character will be struck by a force slightly off center from the driving force, and the hammer will thus tend to pivot into the blank space. Although the characters extend only slightly above the plane of the drum, it is sufficient to create a couple which is measurable in the range of forces and speeds commonly used in present-day printers. In this respect, the resulting printout of a character of the type having two vertical edges (for example, H, M) will have a distinct variation in density across the face of the printed character. Therefore, it is desirable to provide means on the hammer to compensate for the uneven forces thrust upon the face of the character at the time of impact.

SUMMARY OF THE INVENTION The present invention relates to a high-speed printer and more particularly to a printer having a continuously rotating typedrum and a plurality of hammers along a typeline adaptable for striking the type characters in more than one column on the drum. In this respect, the typedrum is divided into two segments or sectors wherein each column contains characters around one segment or one half of the drum, and the other segment is blank in this column, so that, across the drum, every other column in each segment includes raised characters; that is, with blank columns and columns of type alternating across the drum. Of the two sectors of the drum, for descriptive purposes it will be assumed that the odd-numbered columns of type are in one sector, and the even-numbered columns are in the other.

With each hammer being constructed to span two columns, one characterized and one blank, the support and driving force for the hammer is positioned centrally, with the result that, when the hammer is driven against the drum, one side or end portion of the impact tip strikes a character, and the other, or opposite, such portion strikes a blank. The face or impact tip of each hammer is wide enough so that it will print in either of two columns, as determined by the sectors of the typedrum, during the respective time periods a character is presented at the typeline. At the time of impact, the hammer is in a free flight condition, so that rigid. control of the impact tip cannot be precisely maintained, and, because the character is struck off center from the driving force, a measurable couple is set up which tends to pivot the impact tip about the inner edge or portion of the character. As a result of this tendency to pivot about the inner edge, the printing force at this edge of the character is greater, and the print is of higher density, that at its other, or outer, edge, which is farther from the center of the hammer. Therefore, the character is not subject to equal forces across its face, and the print varies in density, with resulting light and dark lines.

The present invention provides an impact tip for a print hammer which is sufficiently wide to span two columns of characters, the tip having a frontal surface curvature wherein the tip area farthest from the central driving force or support strikes the outer portion of the character slightly prior to the striking of its inner portion, nearer the support. In this manner, the farthest portion of the character is struck first, with a slightly greater force, and the tendency to pivot about the edge nearer the center of the hammer completes the impact, so that a more uniform print density is accomplished. Depending upon which sector of the drum is in position for printing, the hammer strikes one character at a time either with the right side of the impact surface or with the left side of the surface relative to the hammer central driving force. If the right side strikes a character, the left side strikes against a blank space, and vice versa.

In view of the above discussion, the principal object of the present invention is to provide an improved print hammer impact tip to insure uniform printing.

Another object of the present invention is to provide a more uniform print with a print hammer which is capable of spanning two columns.

A further object of the present invention is to provide an impact tip for a print hammer spanning two character columns wherein one portion of the tip strikes a character portion prior to the striking of an adjacent and remaining portion of the character.

An additional object of the present invention is to provide a print hammer impact tip having a curvature on one face thereof for producing a more uniform print density.

Another object of the present invention is to provide a print hammer impact tip having a face curvature to compensate for uneven forces across the tip at the moment of impact.

Additional advantages and features of the present invention will become apparent and fully understood from a reading of the following description, taken together with the annexed drawing, in which:

FIG. 1 is a view of a typedrum showing a representative arrangement of type characters thereon, and the lineup of print hammers;

FIG. 2 is a development of a portion of the typedrum of FIG. 1 and also shows the configuration of the print hammer tips;

FIG 3 is a fragmentary side view showing a portion of a print hammer assembly positioned in relation to the typedrum;

FIG. 4 is a view taken on the line 4-4 of FIG. 3;

FIG. 5 is a top view of the assembly shown in FIG. 3;

FIG. 6 is an enlarged view of the hammer tip portion taken on the line 6-6 of FIG. 4; and

FIG. 7 is a top view of the hammer tip shown in FIG. 6, and also shows the relationship of associated parts in greater detail.

Referring to FIG. 1, there is shown a cylindrical typedrum 10, whose peripheral surface carries a plurality of side-by-side type columns 11,12 and is divided into two semicircular sectors or segments 14 and 16. Each type column of the drum 10 includes a portion which has type characters thereon and a portion which is blank. In the two-sector configuration, the odd-numbered columns of type 11 are in one sector 14, and the even-numbered columns 12 are in the other sector 16. Further describing the typedrum columns, the blank columns and the columns of type alternate across the drum, so that a column of type in one sector lines up with a blank column in the other sector.

Suffice it to say that the typedrum is a part of the printing mechanism, which also includes the print hammers and solenoids which drive the hammers towards the typedrum under suitable selective controls. Of course, an ink ribbon travels in a path past the drum, and paper is placed between the hammer and the ribbon, so that, when a solenoid is fired, it drives the hammer, which, inturn, drives the paper against the ribbon and the typeface, leaving an impression, or imprint, on the paper. In this aspect, the solenoid drive and control is determined by the appropriate circuitry for high-speed printers with which the present invention may be used.

The type drum 10 is continuously rotated on a shaft 18 journaled in a typeline assembly frame and driven by a suitable drive motor (not shown). Type faces or characters 20 are etched on the surface of the drum by well-known means, the numerals l to 4 and the letters A to D being representative, as shown in FIGS. 1 and 2. The numerals, the letters, and other type characters are generally not in sequential fashion; however, for the purposes of this application, it is significant that blank columns separate the character columns across the drum, as shown. The surface of a standard such type drum may carry one hundred and thirty-five columns of type, with sixty-four characters in each column, and wherein all the characters would be etched in alternate columns in one sector 14 or 16 and all the characters etched in the adjacent columns of the other such sector. It is understood that each character column contains the 64 alpha-numeric characters, so, in this respect, a print hammer spanning the two columns 11 and 12 is capable of imprinting all of the characters in one halfrevolution of the drum 10.

As seen in FIGS. 1,3, and 5, a plurality of print hammers 22, each including a central support 24, are positioned along the usual typeline for impact with the characters an the drum 10. Several of the hammers 22 may be attachably grouped on a hanger 25, with the individual hammers themselves each carried by an interconnected hammer spring 26. As understood from FIG. 3, each hammer 22, when fired by its solenoid (not shown), is driven towards the drum 10 and carries the paper 27 and the ribbon 28 with it to contact a type character 20. When so driven towards the drum 10, the hammer is actually in a state of free flight by reason of its spring-26-carried central support 24, the driving force being generally centralized along said support. In this free-flight state of the hammer 22 at the time of impact, there is created a force couple as the hammer strikes a character 20 by reason of the fact that, since the hammer spans two columns, its impact tip portion 30 strikes the raised character first, as best understood from FIG. 5, and tends to pivot into the blank space of the adjacent column. Therefore, some of the print force at an outer edge of the impact tip 30 will be given up by the tendency to pivot about an inner edge of the character, while the print force at the edge of the characters nearer the centerline of the hammer will be more directly opposing the centralized force of the hammer and hence will be of higher magnitude. It is thus seen that there is a variation in the impact force across the face of the character by reason of the hammers spanning the two columns.

FIG. 2, 5, and 7 show the configuration of the impact tip 30 making up the present invention where the face of the tip has a curvature which is concave in relation to the end of the hammer 22. Each hammer tip 30 has a dimension in one direction (FIG. 3) slightly greater than the height of a character 20, and a dimension in the other direction sufficiently wide to span two adjacent character columns 11 and 12 (FIGS. 1 and 2). In essence, the face of the impact tip 30 is curved in a direction laterally along the drum 10 and extending towards the ends thereof to compensate for the tendency of the hammer to pivot it into the blank columnar space. As seen in FIG. 5, the hammer 22 may be so positioned in relation to a column of characters that the left portion of its impact tip strikes a character in one sector 14 of the drum upon rotation of the drum, while the right portion of the tip strikes a character in the other sector 16 of the drum, it being noted that the portion of the tip not being used for impact with a character at any one instant will extend into a blank column space.

For purposes of illustration, an impact tip 30 of the present invention would have an outer and an inner curved impact portion on each side of its centerline. The resulting curved face 32 would be divided into a left, outer portion 34 (FIG. 2), a left, inner portion 36, a right, inner portion 38, and a right, outer portion 40. These portions are seen enlarged in FIG. 7 in relation to representative characters 20. When one of the hammers 22 is driven towards the drum l0 and, for example, one of the characters C, D, 3, 4, etc., in the odd-numbered column 11 is to be printed, the portion 34 of the face 32 will strike the left edge of the character slightly prior to the portion 36 striking its right edge. Similarly, the portion 40 will strike the right edge of the character in the even-numbered column 12 slightly prior to the portion 38 striking its left edge.

This slight delay in impact due to the curvature of the impact tip face compensates for the tendency of the hammer tip 30 to pivot into the adjacent blank space because of the striking of the character off center of the central driving force. The result is a more uniform print across the width of the character, with all of the imprinted lines and curves of even density.

It is thus seen that herein shown and described is a pring hammer impact tip which includes all the advantages and features mentioned above. While only one embodiment has been disclosed, slight variations on the above may, of course, occur to those skilled in the art, so it is contemplated that all such variations having these features are within the scope of the invention.

1 Claim:

1. In a printer, a typedrum having a plurality of columns of type characters on the periphery thereof, each column having a portion with type characters thereon and a portion which is blank, with the blank portions of each of the columns being positioned adjacent the type portions of the respective columns contiguous thereto, and a print hammer centrally supported and capable of spanning the space of two of the columns upon engagement with the typedrum and including an impact tip having a curvature for engaging with a portion of one character in one column prior to engaging with another portion of the same character upon impact of the hammer so that the density of an imprint therefrom is substantially uniform across the face of the printed character.

2. In the printer of claim I where said tip curvature extends across the space of a character portion of a column and a blank portion of an adjacent column in a direction along the typedrum.

3. In the printer of claim 1 wherein said curvature extends across the space of a character portion of a column and a blank portion of an adjacent column and assumes a shape in which normals to the curve converge on a plane along the typedrum.

4. In a printer having means for providing uniform density of printed characters. a rotary typedrum with columns of characters thereon. each column having a portion with type characters and a portion which is blank, with the blank portions of each of the columns being positioned adjacent the type portions of the respective columns contiguous thereto, and a centrally supported print hammer capable of striking against the surface of the typedrum and spanning the space of two of the columns, the improvement comprising an impact tip on said hammer, said tip having a curvature starting on a plane at one edge thereof, receding to the midpoint of the tip to a plane farther from the surface of the typedrum than the first-mentioned plane, and advancing to said first-mentioned plane at the opposite edge, whereby a portion of the tip adjacent said one edge strikes part of one character prior to the time a portion of the tip adjacent the midpoint strikes another part of the same character.

5. In the printer of claim 4 wherein said tip curvature is concavely shaped in a direction toward the surface of and along the typedrum.

6. In the printer of claim 4 wherein said tip curvature uniformly spans the space of a character portion of one column and a blank portion of an adjacent column and assumes a shape in which normals to the curve converge in a direction along the typedrum 7. In a high-speed printer having a continuously rotating typedrum carrying a plurality of columns of characters each column having a portion with type characters and a portion which is blank, and print hammers centrally supported and adaptable to be driven towards said typedrum, each hammer being capable of spanning a column of characters and a blank portion of an adjacent column, the improvement comprising a hammer impact tip having an elongated surface extending in a direction along the drum so as to span a character column and a blank portion, said surface having a curvature uniformly receding from each end thereof and convergently normal to the curvature of the typedrum whereby one portion of a character in one column is struck by said impact tip prior to the striking of another portion of the same character thereby.

8. In a high-speed printer in accordance with claim 7 wherein the curvature of the surface assumes a concave shape.

9. In a high-speed printer having a rotatable typedrum divided into sectors with characters embossed on the peripheral surface thereof, the characters being arranged in columns with one sector of columnar characters being offset from another sector of columnar characters, said character columns being spaced by blank portions, a plurality of a print hammers adaptable to be driven against the typedrum, each of said hammers being capable of spanning a character column and a blank portion in a respective sector of the typedrum, an impact tip for each print hammer. the tip having a surface extending in one direction to cover a character width and an adjacent blank space and in the other direction to cover a character height, the surface having a curvature starting on a plane at one end of the tip and extending in the first-mentioned direction, receding from the plane to a maximum midway between the ends of the tip surface to a plane farther from the typedrum surface than the first-mentioned plane, and advancing to said first-mentioned plane at the other end of the tip whereby an outer portion of the impact tip surface strikes one edge of a character prior to an inner portion of the tip striking another edge of the character.

10. In a high-speed printer in accordance with claim 9 wherein the tip surface assumes a concave shape in the first mentioned direction and normal to the curvature of the typedrum.

11. In a high-speed printer having a rotary typedrum divided into sectors, characters arranged in sector columns on the face of the drum, one sector of columnar characters being offset from another sector, and each column of characters being separated from its adjacent column by a blank portion therebetween, and a print hammer centrally supported and adaptable to be driven into contact with said drum and formed to span a column of characters and a blank portion, the combination including an impact tip on said hammer extending across the face thereof laterally along the typedrum and having a surface curvature starting on a plane at one edge of the tip, uniformly receding in a direction toward the hammer support to a midpoint of the tip to a plane farther from the face of the drum than the first-mentioned plane, and unifonnly advancing to said first-mentioned plane at the opposite edge of the tip whereby one side of the tip face makes contact with a character at the time the other side spans a blank space and, by reason of the curvature of the tip face, one portion of a character is struck prior to the striking of another portion of the same character.

12. In the printer of claim lll wherein the surface curvature of the impact tip assumes a concave shape in relation to the hammer support and in which normals to the curve converge in a direction along the typedrum. 

1. In a printer, a typedrum having a plurality of columns of type characters on the periphery thereof, each column having a portion with type characters thereon and a portion which is blank, with the blank portions of each of the columns being positioned adjacent the type portions of the respective columns contiguous thereto, and a print hammer centrally supported and capable of spanning the space of two of the columns upon engagement with the typedrum and including an impact tip having a curvature for engaging with a portion of one character in one column prior to engaging with another portion of the same character upon impact of the hammer so that the density of an imprint therefrom is substantially uniform across the face of the printed character.
 2. In the printer of claim 1 where said tip curvature extends across the space of a character portion of a column and a blank portion of an adjacent column in a direction along the typedrum.
 3. In the printer of claim 1 wherein said curvature extends across the space of a character portion of a column and a blank portion of an adjacent column and assumes a shape in which normals to the curve converge on a plane along the typedrum.
 4. In a printer having means for providing uniform density of printed characters, a rotary typedrum with columns of characters thereon, each column having a portion with type characters and a portion which is blank, with the blank portions of each of the columns being positioned adjacent the type portions of the respective columns contiguous thereto, and a centrally supported print hammer capable of striking against the surface of the typedrum and spanning the space of two of the columns, the improvement comprising an impact tip on said hammer, said tip having a curvature starting on a plane at one edge thereof, receding to the midpoint of the tip to a plane farther from the surface of the typedrum than the first-mentioned plane, and advancing to said first-mentioned plane at the opposite edge, whereby a portion of the tip adjacent said one edge strikes part of one character prior to the time a portion of the tip adjacent the midpoint strikes another part of the same character.
 5. In the printer of claim 4 wherein said tip curvature is concavely shaped in a direction toward the surface of and along the typedrum.
 6. In the printer of claim 4 wherein said tip curvature uniformly spans the space of a character portion of one column and a blank portion of an adjacent column and assumes a shape in which normals to the curve converge in a direction along the typedrum.
 7. In a high-speed printer having a continuously rotating typedrum carrying a plurality of columns of characters each column having a portion with type characters and a portion which is blank, and print hammers centrally supported and adaptable to be driven towards said typedrum, each hammer being capable of spanning a column of characters and a blank portion of an adjacent column, the improvement comprising a hammer impact tip having an elongateD surface extending in a direction along the drum so as to span a character column and a blank portion, said surface having a curvature uniformly receding from each end thereof and convergently normal to the curvature of the typedrum whereby one portion of a character in one column is struck by said impact tip prior to the striking of another portion of the same character thereby.
 8. In a high-speed printer in accordance with claim 7 wherein the curvature of the surface assumes a concave shape.
 9. In a high-speed printer having a rotatable typedrum divided into sectors with characters embossed on the peripheral surface thereof, the characters being arranged in columns with one sector of columnar characters being offset from another sector of columnar characters, said character columns being spaced by blank portions, a plurality of a print hammers adaptable to be driven against the typedrum, each of said hammers being capable of spanning a character column and a blank portion in a respective sector of the typedrum, an impact tip for each print hammer, the tip having a surface extending in one direction to cover a character width and an adjacent blank space and in the other direction to cover a character height, the surface having a curvature starting on a plane at one end of the tip and extending in the first-mentioned direction, receding from the plane to a maximum midway between the ends of the tip surface to a plane farther from the typedrum surface than the first-mentioned plane, and advancing to said first-mentioned plane at the other end of the tip whereby an outer portion of the impact tip surface strikes one edge of a character prior to an inner portion of the tip striking another edge of the character.
 10. In a high-speed printer in accordance with claim 9 wherein the tip surface assumes a concave shape in the first mentioned direction and normal to the curvature of the typedrum.
 11. In a high-speed printer having a rotary typedrum divided into sectors, characters arranged in sector columns on the face of the drum, one sector of columnar characters being offset from another sector, and each column of characters being separated from its adjacent column by a blank portion therebetween, and a print hammer centrally supported and adaptable to be driven into contact with said drum and formed to span a column of characters and a blank portion, the combination including an impact tip on said hammer extending across the face thereof laterally along the typedrum and having a surface curvature starting on a plane at one edge of the tip, uniformly receding in a direction toward the hammer support to a midpoint of the tip to a plane farther from the face of the drum than the first-mentioned plane, and uniformly advancing to said first-mentioned plane at the opposite edge of the tip whereby one side of the tip face makes contact with a character at the time the other side spans a blank space and, by reason of the curvature of the tip face, one portion of a character is struck prior to the striking of another portion of the same character.
 12. In the printer of claim 11 wherein the surface curvature of the impact tip assumes a concave shape in relation to the hammer support and in which normals to the curve converge in a direction along the typedrum. 